&1.relative_identifier(
  &2,
  key: &3
)
&1.relative_identifier(
  &2,
  key: &3
)(
  &4,
  key: &5
)
&1.relative_identifier key: &2
&1.relative_identifier unqualified &2,
                                   key: &3
&1.relative_identifier &2,
                       key: &3